linux-kernel - Re: [PATCH 0/3]CFQ: add think time check for service tree and group

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Date:	Mon, 11 Jul 2011 13:44:05 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	Jens Axboe <jaxboe@...ionio.com>, Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [PATCH 0/3]CFQ: add think time check for service tree and group

2011/7/4 Shaohua Li <shaohua.li@...el.com>:
> Hi,
>  Currently when the last queue of a service tree/group is empty, CFQ
> doesn't expire the queue. This is to allow requests from the tree/group
> come soon, so tree/group doesn't miss its share. But if the think time
> is big, the assumption isn't correct. idling the queue is just wasting
> bandwidth.
>
> Originally I was hoping this can resolve Vivek's fsync issue, but it
> doesn't. The fsync issue is caused by queue idling. But since think time
> check only helps for think time above default queue idle time (8ms),
> think time check doesn't help.
>
> On the other hand, think time check is still helpful for queues with
> think time. I had test case in follow patches show throughput
> improvement without sacrifice tree/group shares.
>
Jens,
can you look at the patches? I refreshed some patches in replying
Vivek, I can resend if required.

Thanks,
Shaohua
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